I've learned a ton more by losing in III.4 than I did winning in D IV, however, it is possible to stick in DIII and transition well from D IV.
You may currently be: a bit shocked at the talent gap, short on cash, and have no idea on how to match up versus your opponent, but that has nothing to do with the competitive nature of D4, or with a small promotion bonus. It has solely to do with how you manage the economics of this game. I was routinely selling out in D4 and came to D3 with a surplus of cash. Had I been a tad more patient, and had I not overpaid (2MM) for a player who's best attribute is prominent passing I could have easily made the adjustments that I needed to (see EC Flyers 2nd half moves last season), and remained in the league.
Frankly I'm excited to focus on training the things that I need to train, but more excited to get back to the basics in my game planning. The managers of III.4 are top notch; they understand all facets of the game. In D4 you could take a few games off, but here you can't.
Accept the challenge to better your team instead of telling people to "GTFO with their BS". Its rude, presumptive and its inconsistent with how the other managers (whom you'll soon be playing against), treat each other.